1. Field of the Invention
The present invention relates to a logic circuit for board power-supply evaluation and a board power-supply evaluating method for evaluating power-supply system of a printed circuit board loaded with a rewritable semiconductor integrated circuit device (hereinafter, “logic device”) such as a field programmable gate array (FPGA).
2. Description of the Related Art
Logic devices to be loaded on printed circuit boards (hereinafter, “product boards”) used in electronic apparatuses such as communications apparatuses, information apparatuses, and control apparatuses includes sequential circuits and combinational circuits, wiring areas/wiring switches, and the like, and by connecting those in combination, various functions according to the respective apparatuses have been realized.
Meanwhile, recently, there has been considerable increase in the scale (multiple pins) and reduction in required voltage of logic devices. As a result, in the product boards loaded with those logic devices, there have been reported occurrence of malfunction, such as an operation reset of the logic device or an abnormal output signal, due to voltage drop or ripple, a high-frequency noise (hereinafter, “power-supply system noise”), or the like. Therefore, when designing a power-supply system of a product board, power consumption of a logic device to be loaded is either calculated or predicted, and based on that data, capacitance, arrangement, and the like of a power-supply circuit and a bypass capacitor element are designed.
As the method for calculating or predicting the power consumption of a logic device, conventionally, a method for calculation by emulating a logic circuit incorporated in a product board by use of a dedicated evaluation device, which includes an emulator, a power unit, and a measuring unit (for example, Patent Document 1), has been employed.
Patent Document 1: Japanese Published Unexamined Patent Application No. 2001-222561
However, despite designing of a product board by estimating the power consumption of the logic device by logic simulation after a detailed design of a logic circuit as in the above, is was not possible to prevent the occurrence of the malfunction mentioned above.
For identifying the cause of occurrence of the malfunction, although it is necessary to distinguish whether there is a problem in a power-supply design of a product board or in a board circuit design such as timing, this is not easy. Moreover, although there is a method for evaluating a logic device alone by use of an evaluation board, there is no method for evaluating a power-supply system in operation of a logic device that has been loaded on a product board, namely, a logic device programmed so as to realize a function of an electronic apparatus to be applied.